### Another example

parent d3a23521
 ... ... @@ -897,46 +897,46 @@ WHERE ST_SquareGrid Returns a set of grid squares and cell indices that completely cover the bounds of the geometry argument. setof record ST_SquareGrid float8 size geometry bounds ST_SquareGrid Returns a set of grid squares and cell indices that completely cover the bounds of the geometry argument. setof record ST_SquareGrid float8 size geometry bounds Description Description Starts with the concept of a square tiling of the plane. For a given planar SRS, and a given edge size, starting at the origin of the SRS, there is one unique square tiling of the plane, Tiling(SRS, Size). This function answers the question: what grids in a given Tiling(SRS, Size) overlap with a given bounds. Starts with the concept of a square tiling of the plane. For a given planar SRS, and a given edge size, starting at the origin of the SRS, there is one unique square tiling of the plane, Tiling(SRS, Size). This function answers the question: what grids in a given Tiling(SRS, Size) overlap with a given bounds. The SRS for the output squares is the SRS provided by the bounds geometry. Doubling or edge size of the square generates a new parent tiling that perfectly fits with the original tiling. Standard web map tilings in mercator are just powers-of-two square grids in the mercator plane. The SRS for the output squares is the SRS provided by the bounds geometry. Doubling or edge size of the square generates a new parent tiling that perfectly fits with the original tiling. Standard web map tilings in mercator are just powers-of-two square grids in the mercator plane. Availability: 3.1 Availability: 3.1 Example: Counting points in squares To do a point summary against a square tiling, generate a square grid using the extent of the points as the bounds, then spatially join to that grid. SELECT COUNT(*), squares.geom FROM Example: Counting points in squares (using single chopped grid) To do a point summary against a square tiling, generate a square grid using the extent of the points as the bounds, then spatially join to that grid. Note the estimated extent might be off from actual extent, so be cautious and at very least make sure you've analyzed your table. SELECT COUNT(*), squares.geom FROM pointtable AS pts INNER JOIN ST_SquareGrid( ... ... @@ -944,16 +944,31 @@ FROM ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857) ) AS squares ON ST_Intersects(pts.geom, squares.geom) GROUP BY squares.geom GROUP BY squares.geom See Also , Example: Counting points in squares using set of grid per point This yields the same result as the first example but will be slower for a large number of points SELECT COUNT(*), squares.geom FROM pointtable AS pts INNER JOIN ST_SquareGrid( 1000, pts.geom ) AS squares ON ST_Intersects(pts.geom, squares.geom) GROUP BY squares.geom See Also , , , ... ...
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